His biggest weakness was that he lacked the mauler size that most teams in the NFL want at the tackle positions.
He's a finesse and technique player, and a very good one at that, but fewer NFL offenses use the lighter, faster tackles these days.
Even though he was listed as 300 lbs, that's a rather optimistic estimate, since he was playing close to 290 lbs during most of his college career.
He's also maxed out on his frame, since he's a very slender fellow for someone of his size.
He wasn't going to get any bigger, and I actually agree with his decision to go pro, due to the risk of injuries, etc.
It would have been nice to have been a draft pick, but this way, as a free agent, Mr. Wagner did make a good choice with the Titans.
Brian Daboll (part of the Belichick coaching tree), runs a modified Erhardt-Perkins offense, so this scheme has plenty of options for lighter, more agile linemen.